ZOOLOGY. 



By Prof. Theodore Gill. 



INTRODUCTION. 



The laborers in the various fields of Zoology have prosecuted investi- 

 gations in the year 1885 with undiminished ardor, and scarcely anj' 

 department has been neglected. The tendency manifested for some 

 years towards a special study of embryology and of animals from an 

 embryological standpoint, has been continued. Systematic zoology, on 

 the other hand, has at least maintained its course during the period, 

 and some most valuable works have appeared. Among such may be 

 especially mentioned the lirst two of the comtemplated tliree volumes 

 of a catalogue of the Lacertilian reptiles in the British Museum, by Dr. 

 George Edward Boulenger. A number of works on extinct animals, iu 

 which groups have been systematically considered, have been also pub- 

 lished. Doubtless the most important and interesting of these for the 

 American zoologist are (1) the enormous volume by Prof. E. D. Cope 

 on The Vertebrata of the Tertiary Formations of the West (Part i), and 

 (2) Prof. O. C. Marsh's beautifully illustrated and printed "Diuocerata, 

 a monograph of an extinct order of gigantic mammals." Both of these 

 volumes do indeed purport on their title pages to have been printed in 

 previous years, Cope's work bearing the imprint of 1883 and Marsh's 

 that of 1884, but they were not really published or accessible to the pub- 

 lic till early in 1885. 



As in the previous reports, the language of the original from which 

 the abstract is compiled is generally followed as closely as the case 

 will permit. It has, however, been found necessary to limit the ab- 

 stract to the illustration of the prominent idea underlying the original 

 memoir, and pass by the proofs and collateral arguments. At the 

 same time it has been often attempted to bring the new discovery into 

 relation with the previous status of information respecting the group 

 under consideration. As to the special discoveries recorded, they have 

 been generally selected (1) on account of the modifications the forms 

 considered may force on the system ; or (2) for the reason that they are 

 or have been deemed to be of high taxonomic importance ; or (3) because 

 the animals per se are of general interest; or, finally (4), because they 



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